The invention relates to an external bone-anchoring element.
External anchoring of bones is an old surgical technique which was first used a century ago. Its application has for a long time been limited to complicated fractures in traumatology and consequently in orthopedics, i.e. the secondary treatment of fractures, infections slow knitting of the bones, pseudarthroses, difficult bone-settings, etc.
External anchoring is used more particularly for long bones such as the femur, the tibia, the humerus, the radius, the cubitus and, in particular, the bones in the leg.
It is desirable to be able to extend the use of the external anchoring means to the pelvic basin, the clavicle, to joints such as the knee, elbow and shoulder, and to the skull for the treatment of the cervical and lumbar vertebrae, etc.
It is also desirable to manufacture small anchoring means which can be used on small bones, such as the metatarsals and the metacarpals, and in maxillofacial surgery as well as in experimental surgery on small animals.
External bone-anchoring elements enable two kinds of bone-anchoring to be carried out:
transfixing anchoring, wherein the pins extend from one side of the limb to the other, and
non-transfixing anchoring, wherein the pins are introduced into the bone without completely transversing it. Transfixing anchoring, which is mostly used on the leg, is more rigid than non-transfixing anchorage.
Fitted at both sides of the leg are two rods or frames which are anchored on two groups of pins disposed on either side of the fracture. The two frames or the two rods are interconnected by a brace which is as stable as possible and which may comprise sliding rods or bars, the length of which can be increased or reduced.
External anchoring means made up of rings are also in existence. Such anchoring means are described for example in Swiss Patent Nos. 579,385 and 596,826 which relates to the use of external anchoring means using the "Russian" method. The anchoring means described in these two patents are based solely on the use of circles. These are therefore the circles which form the frames and the braces. These circles can be single or double, i.e. they may surround the bone. It is thought that the single circle will be mostly used if there are two groups of parallel pins on each bone fragment. In certain cases, a different problem arises. If the bone fragment is very short, i.e. near a joint, and the fragment is not long enough to allow two or three parallel pins to be secured, use may be made of another method, such as that described by the Russians, in which method a very short bone fragment can be anchored by providing a circular support on which are secured smooth transfixing intersecting pins (see Swiss Patent No. 579,385). This patent discloses a device for interconnecting the various rings. But this device is very complicated in its manipulation and it, therefore, does not permit the fracture to be readily set.
Another manufacturer, Kronner, uses a plastic, circular arrangment of which parallel transfixing pins are fitted. This device is also different to use since the pins are offset in relation to the circle. Setting is rendered easier, since the connecting bars are mounted on swivel joints. However, based upon tests that have been performed, the inventor hereof, the immobilizing system using swivel-joints may permit sliding after setting.
All these systems have one point in common, i.e. that of enabling the bone fragments to be moved away or towards each other as required (retraction of compression).
As a general rule, anchoring means based solely on the use of circles can be extended to apply to the clavicle only with difficulty.